migrants arriving to late leaf out

[Scott E. Severs]

During survey work this AM I was struck by the state of slow leaf out in the cottonwoods. It made for amazing observing conditions for arriving migrants, and it seems many species will arrive before well ahead of the majority of leaf out, making for great but odd observing conditions. I was especially struck by seeing Warbling Vireos and Orchard Orioles on bare branches today!

--Scott

Scott E. Severs
Longmont, CO

[Scott E. Severs]

Sorry everyone - I forgot to say I was in St. Vrain State Park.

--Scott

Scott E. Severs
Longmont, CO

[DAVID A LEATHERMAN]

Scott et al,
Yes, this feels like a strange spring in terms of budbreak on woody plants and the arrival timing of various neotropical migrants.  But we say that, in respect to some aspect of it somewhere in CO, every year, don't we?  The plant people have their own listserv called "PestAlert" (run by my buddy Whitney Cranshaw at CSU) and they have been discussing this same phenomenon from the plant perspective.  This year's plant development took several setbacks in April, both in the form of cold temps and snow.  But I find it interesting that as of about a week ago,  the quantitative measurement of where we stand in terms of accumulated heat units for 2013 plant development (referred to as "degree-days") puts us basically right at the 30-year average for early May.  We, including me, tend to forget the last few years have been exceptionally early.  As with climate change in general, such annual fluctuations and extreme phenomena like 4 feet of snow in April, make it difficult to truly assess long term trends.  Just as the birds coped with the storms very well on their own (without genuine need for massive intervention on our part such as artificial feeding), the plants will, too (for the most part).  We birders can, likewise, adjust and enjoy seeing birds without leaves in the way. 

In another week of warm/hot weather, leaf elongation will probably hide the late migrants and things will look pretty "normal", whatever that is in CO?

Dave Leatherman
Fort Collins

---

From: scotte...@gmail.com
Date: Tue, 14 May 2013 12:05:01 -0600
Subject: [cobirds] migrants arriving to late leaf out
To: cob...@googlegroups.com

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[Norm Erthal]

Dave’s information is interesting in how typical it is for us to discount previous events when we discuss current events. An important fact to also note is the mention of the use of a 30 year average of the temperatures in the evaluation. This lessens the actual change in this year’s temperatures. The last three decades have been warmer than the average of the entire historical record. What this means is this year is still warmer than the long term average. We face the same error when the present snowpack is evaluated. It also uses a thirty year running average. The current thirty year average is also in decline compared to the historic record. The current snowpack of the Platte River basin being 120 % of average could in reality be less than the average over a longer period. To carry this further, the current level of atmospheric CO2 of over 395 ppm would be only 25 ppm above the average of the last thirty years while it is 115 ppm over the average high of the interglacial periods for the last 720,000 years and the average prior to the industrial revolution.

Norm Erthal

Arvada, CO

[Larry Modesitt]

Very good point, Norm. A huge jump next year of 100 ppm of CO2 shows only a change of 3 ppm on the 30 year average. No wonder that we hear of a small change and discount it as insignificant. Do they use 30 year running averages for ocean temperatures also?

Larry Modesitt

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[Norm Erthal]

Larry raises a good question about ocean temperatures. I do not have an answer for that. Another area where there is a much shorter period of data is Arctic sea ice extent. The data only extends to 1979. This is because the use of satellites in gathering the data. The years from 2007 through 2012 are all below what is a 32 year average. What is more revealing is all of them are well below two standard deviations less than the average and approach four standard deviations For this to be the case, there would need to be several years of above average to put the average where it is. This year is on pace to continue this streak. What is also of note is the average age and thickness of sea ice is also in a marked decline. For older data, we have only anecdotal information from early explorers and more current information from scientific expeditions. I have not seen a compilation of this.

 

Norm Erthal

Arvada, CO